Finish with a boy, but not completely (4)
I believe the answer is:
half
'not completely' is the definition.
I can't tell whether this definition defines the answer.
'finish with a boy' is the wordplay.
'finish' says to take the final letters.
'a boy' becomes 'alf' (I've seen this before).
The final letter of 'with' is 'h'.
'h'+'alf'='HALF'
'but' acts as a link.
Can you help me to learn more?
(Other definitions for half that I've seen before include "alcoholic drink" , "little drink" , "Short distance - steal!" , "one over a couple" , "proportion" .)